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BitDevs Meetup 8

Topics:

Core Dev:

• Selfish Mining - Overwrought Criticism

• Off-chain anonymous transactions by secure transfer of private keys

• CoinSwap

• Extending the Payment Protocol with vCards

• P2Pool Upgrades

• High-speed Bitcoin Relay Network

• Reduce latency in network processing

• Implementing CoinJoin in main client?

• OSX 10.9 Mavericks AppNapp & Bitcoin-QT Issues

• DoS-ban on blocks that contain invalid proof-of-work


Tools:

• Raw TX Tool Written in Java

• CoinJoin Blockchain.info implementation now in the wild

 

Presentations:

• Max H - BitDeliver

• Charles Hope, Dan Patterson - EarlyTemple

As always, if you've got something you'd like to present just shoot me an email and come prepared.

Join or login to comment.

  • Hernan.S

    Hey guys don't forget today we are having our crypto-currency trading workshop http://bitcoinclass.eventbrite.com

    1 · November 22, 2013

  • Ee

    Again, even at 25% the entire network's computing power, a single perpetrator probably won't recover equipment costs from mining rewards, so the attack really requires the cooperation of those already mining. Here's where game theory comes into play. Such a conspiracy resembles the Prisoner's Dilemma. http://en.wikipedia.org/wiki/Prisoner%27s_dilemma

    If we limit the number of players in the Prisoner's Dilemma to 2, the penultimate scenario for any single player is for both players to cooperate. The ultimate scenario is for one player to defect and betray the cooperating player. This dilemma plagues all conspiracies, as we saw with Eric Snowden, and his defection against the NSA. Granted, most real life Prisoner's Dilemma scenarios allow opportunities for revenge against defectors. However, real life frequently offers defectors escape from such revenge, as Snowden has so far found.

    November 14, 2013

    • Ee

      I realize you're not disagreeing with an adjustment of the 25% figure, but I do have to clear up some misinformation.

      In an iterated Prisoner's Dilemma, it is NOT the dominant strategy to defect first. You're probably thinking of single-shot, one-move, no reprisal Prisoner's Dilemma.

      http://en.wikipedia.o...­

      As per the Wiki page, the Tit-for-Tat strategy is held to be the most robust for the most basic iterated Prisoner's Dilemma. It has these attributes:
      1. Nice (that is to NEVER be the first to defect)
      2. Retaliatory
      3. Forgiving
      4. Non-envious

      This was determined by computer simulations done in the early 80's. Since then, only a change of rules has allowed other strategies to consistently beat Tit-for-Tat.

      November 15, 2013

    • devaang

      I see your point. I was referring to a continuously iterated dilemma which I see now is inaccurate, since each selfish block found can be considered a discrete decision node. The likelihood of a tit/tat strategy emerging at the 25% level is low - given the number of actors required to participate, probably anonymously, the requirement of forgiveness would be hard to fulfill. My point is that selfish mining is unlikely unless done by a single large entity such as a government.

      November 15, 2013

  • Ee

    I've been intrigued by the Selfish Mining attack since reading about it earlier this month. Vitalik Buterin, one of my favorite commentators, gave a mathematical breakdown of the attack in http://bitcoinmagazine.com

    http://bitcoinmagazine.com/7953/selfish-mining-a-25-attack-against-the-bitcoin-network/

    Indeed, the math points to a lowering of the computing power necessary to attack the Bitcoin protocol. However, it really needs to consider game theory to arrive at the 25% figure. Justin mentioned there was a game theoretical analysis already done on this, but I didn't search the Web for any such thing, so forgive me if this sounds identical since no sources are referenced.

    November 14, 2013

  • Ee

    Firstly, Buterin calls the Selfish Mining attack an economic attack. It's not cited explicitly in his post, but I think the reason is that perpetrators seek to gain a direct monetary payoff from the attack. This is in contrast to a 51% attack, which only really destabilizes the system. The monetary payoff from double-spending as a result of a 51% attack probably won't offset the cost of the computing power necessary to mount the attack. Instead perpetrators of a 51% attack would probably benefit more as a result of the downfall of the system (short selling, bragging rights, triumphant authoritarianism, etc.)

    As a quick aside, I find a 51% attack against Bitcoin unlikely due to how lucrative that much computing power would be at this stage. Why kill your neighbor's golden goose when you can steal it?

    November 14, 2013

  • Ee

    I don't see a reasonable method of exacting revenge against a defector in a Selfish Mining attack. The most poorly implemented Selfish Mining attack would have the defector simply broadcast the concealed blocks before anyone else in the conspiracy, and run off with the awarded coins leaving the rest of the conspiracy empty-handed. This sounds like engineering so incompetent, it probably wouldn't happen. More likely, the defector would want to attack the conspiracy due to a disagreement, or expose the conspiracy due to loose lips.

    How would we counter the exposed conspiracy? Launch another Selfish Mining pool. 2 or more selfish actors in any scenario become a game, or in economic terms, a market. Buterin uses the variables X and Z to refer to the probability of finding useful blocks. The more Selfish Mining pools there are, the lower X and Z become, which in turn, make the attack more difficult, eventually turning so-called "Selfishness" into "Decentralization."

    1 · November 14, 2013

  • Hernan.S

    guys check out my twitter feed @crypto_trader i will be posting most my trades there all month

    November 14, 2013

  • Jerry C.

    hey Pat, got that link for the hangout?

    November 12, 2013

  • J

    November 13, 2013

  • Hernan.S

    Hey guys don't forget friday we are having our crypto-currency trading workshop http://www.meetup.com/xtech-mee...­

    November 6, 2013

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